1. Field of the Invention
This invention relates to latch assemblies and, more particularly, to a latch assembly that can be used to releasably maintain a movable closure element in a desired position relative to a support therefor.
2. Background Art
Movable closure elements are used in many industries in both static environments and on moving equipment. These closure elements are commonly pivoted, or translated, between different positions, normally opened and closed positions, to selectively block and allow access to, a space fronted by the closure element.
An exemplary latch assembly, utilized on the above type of closure element, is shown in U.S. Pat. No. 6,158,787, to Kutschat. Kutschat employs two throated rotors 16 which are repositionable to cooperatively engage with a strike element 4. The rotors 16 are designed to be selectively maintained in secondary latched positions, as shown in FIG. 7B, and primary latched positions, as shown in FIG. 7C. The primary and secondary latched positions are maintained by the end of an L-shaped arm 28, which is movable about a pivot 56 between positions wherein the arm 28 is engaged with the rotors 16, to maintain their latched positions, and disengaged from the rotors. The free end of the arm 28 is spaced from the pivot 56 and travels in an arcuate path between its rotor-engaged and rotor-disengaged positions. Accordingly, as the arm 28 is pivoted to effect disengagement, the rotor 16 most remote from the pivot 56 must be pivoted to clear the arcuately moving free end of the arm. As a result, significant resistance to pivoting of the arm 28 may be imparted by the rotor 16.
It is conventional to stamp the rotors from relatively thick metal stock or to form the rotors from metal. Typically, the metal rotors are pivotably mounted on pins/axles within a receptacle defined by facing surfaces of a housing. The thickness of the rotors is normally substantially less than the spacing between the facing housing surfaces. As a result, the pins/axles and/or housing must be provided with support surfaces to maintain the desired axial position of the rotors relative to their associated mounting pin/axle.
Aside from requiring special pins/axles with supporting, axially facing surfaces, the rotors may be prone to skewing relative to their associated pin/axle. Commonly, the contact area between the rotors and pins/axles is relatively small so that a certain degree of skewing is inevitable. Alternative arrangements are known in the art to confine movement and skewing of the rotors. For example, as shown in U.S. Pat. No. 6,158,787, to Kutschat, one of the housing parts has an offset end which is bent to confine the axial rotor shifting. The potential for rotor skewing exists likewise with this design.
By reason of the relatively small contact area between the axially extending surfaces on the rotors and the cooperating pins/axles, these surfaces are prone to considerable wear. Similarly, a catch element, which contacts the rotors to maintain the same in at least a primary latched position, engages the rotors along a relatively short axial distance. To avoid excessive wear, these catches have likewise commonly been made from a metal material.
By having to use metal for the rotors and catch elements, the costs attendant the manufacture of these elements may be relatively high. At the same time, metal parts are prone to corrosion in certain severe environments in which they are used. This may lead to deterioration of the latch assembly components and ultimately to the premature failure of the latch assembly.
Still further, the metal parts generally have a relatively high coefficient of friction between the surfaces which coact. This may lead to binding between the metal parts that are required to act, one against the other.
One problem with existing latch assemblies is attributable to the fact that the closure element must be nearly closed for the rotors to achieve the secondary latched positions. The present design of glass doors on agricultural tractors requires significant camber built in to the door to compensate for the inherent flexing of the door. In addition, all-glass doors require more momentum to be closed to the secondary latched position and some never achieve full closing to the primary latching position. It has been observed that doors can be accidentally left ajar. With the equipment being transported at high speeds, the door can fly open and possibly shatter.
Another problem with the prior art latch assemblies has been that with the conventional latch assembly construction, the secondary latched positions for the rotors may be almost indistinguishable from the primary latched positions by viewing the position of the closure element. As a result, a user may mistakenly believe that the unlatched closure element, which is but slightly ajar, is positioned so that the rotors are in their secondary latched positions. This could lead to a situation in which the unlatched closure element may be inadvertently opened or otherwise undesirably allowed to reposition. There is also a potential problem I the manufacturing and assembly operation that can lead to additional time spent to install the latch and door plus rework and warranty costs to correct this condition in the field.